Statins are a class of pharmaceutical active ingredients inhibitors of the 3-Hydroxy-3-Methylglutaryl-Coenzime A (HMG-CoA) reductase, the enzyme that catalyzes the conversion of HMG-CoA to Mevalonate, a limiting agent of the biosynthesis of Cholesterol and they are therefore used against all the forms of hypercholesterolemia, for the regression of the atherosclerotic plaque and for the prevention of cardiovascular events.
The first statin to be discovered and commercialized was Mevastatin, having the following structure:

After that, other natural statins have been discovered and commercialized as Pravastatin having the following chemical structure:

or such as Lovastatin (in acid form) having the following chemical structure:

All the above statins are characterised in that they comprise a similar dicyclohexyl skeleton bounded with the same seven member alkyl chain, having two hydroxyl groups bounded to two asymmetric carbon atoms. Such chain can be in cyclic “lactone form” or in open “acid form”.
Thus, Lovastatin, is typically present in “lactone form”, being described with the following chemical formula:

wherein both side chain hydroxyls have R configuration.
Another important statin of this type is Simvastatin, typically present in the lactone form, identified with the following structure:

Simvastatin in acid form has the following chemical structure:

wherein both side chain hydroxyls have R configuration.
In the more recent years a new type of statins have been discovered and marketed such as Fluvastatin, Cerivastatin, Rosuvastatin and Pitavastatin.
Rosuvastatin has the following structure formula:

and has chemical name (E)-(3R,5S)-7-[4-(4-Fluorophenyl)-6-isopropyl-2-[(methylsulfonyl) (methyl) amino]pyrimidin-5-yl]-3,5-dihydroxyhept-6-enoic acid. Rosuvastatin is currently marketed as calcium salt (Rosuvastatin calcium), or better as hemicalcium salt and with commercial name of Crestor.
Cerivastatin has the following formula:

Pitavastatin has the following formula:

Fluvastatin has the following formula:

The second type of statins are characterized by a double bond with trans (E) geometry in the side chain.
Many classic synthetic approaches for the synthesis of statins, particularly for those having E geometric isomerism, have been developed during the last decades. Many methods comprise an olefination reaction (Wittig, Horner-Emmons or Julia reactions) carried out between the side chain functionalized by means of phosphorous, phosphorane or sulphone groups with suitable aldehydes comprising the core structure of statins. However all these methods have the drawback that the reaction is not always very selective towards the trans (E) isomer, thus also forming the cis (Z) isomer which is an impurity that is often difficult to remove. Another big drawback is that the side products of the reaction are phosphin oxides or sulphur compounds. These substances are difficult to remove from the reaction mixtures, thus increasing the whole cost of the synthesis of statins. Moreover, the molar weight of phosphorous, phosphorane or sulphone reagents, e.g. triphenylphosfine ylides, is very high when compared with the molecular weight of the side chain and thus the productivity of the process is quite low since it is necessary to handle large amounts of reagents to obtain a relatively low amounts, in terms of kilograms, of products.
An example of this known reaction, directed to the preparation of Rosuvastatin, is described in EP0521471A1, or more recently in WO2009/128091 and WO2009/118598.